Electrochemical Fabrication Methods with Enhanced Post Deposition Processing

ABSTRACT

An electrochemical fabrication process for producing three-dimensional structures from a plurality of adhered layers is provided where each layer comprises at least one structural material (e.g. nickel or nickel alloy) and at least one sacrificial material (e.g. copper) that will be etched away from the structural material after the formation of all layers have been completed. An etchant containing chlorite (e.g. Enthone C-38) is combined with a corrosion inhibitor (e.g. sodium nitrate) to prevent pitting of the structural material during removal of the sacrificial material. A simple process for drying the etched structure without the drying process causing surfaces to stick together includes immersion of the structure in water after etching and then immersion in alcohol and then placing the structure in an oven for drying.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/840,998, filed May 7, 2004, which in turn is a continuation-in-partof U.S. patent application Ser. No. 10/434,294, which was filed on May7, 2003, which in turn claims benefit of U.S. Provisional PatentApplication No. 60/379,134 which was filed on May 7, 2002. Both of thesepriority applications are incorporated herein by reference as if setforth in full.

FIELD OF THE INVENTION

This invention relates to the field of electrochemical deposition andmore particularly to the field of electrochemical deposition eitheradhered masks and/or using conformable contact masks, that are formedseparate from a substrate, to control deposition, such as for example inElectrochemical Fabrication (e.g. EFAB™) where such masks are used tocontrol the selective electrochemical deposition of one or morematerials according to desired cross-sectional configurations so as tobuild up three-dimensional structures from a plurality of at leastpartially adhered layers of deposited material.

BACKGROUND

A technique for forming three-dimensional structures (e.g. parts,components, devices, and the like) from a plurality of adhered layerswas invented by Adam L. Cohen and is known as ElectrochemicalFabrication. It is being commercially pursued by Microfabrica® Inc.(formerly MEMGen Corporation) of Van Nuys, Calif. under the name EFAB®.This technique was described in U.S. Pat. No. 6,027,630, issued on Feb.22, 2000. This electrochemical deposition technique allows the selectivedeposition of a material using a unique masking technique that involvesthe use of a mask that includes patterned conformable material on asupport structure that is independent of the substrate onto whichplating will occur. When desiring to perform an electrodeposition usingthe mask, the conformable portion of the mask is brought into contactwith a substrate while in the presence of a plating solution such thatthe contact of the conformable portion of the mask to the substrateinhibits deposition at selected locations. For convenience, these masksmight be generically called conformable contact masks; the maskingtechnique may be generically called a conformable contact mask platingprocess. More specifically, in the terminology of Microfabrica® Inc. ofVan Nuys, Calif. such masks have come to be known as INSTANT MASKS™ andthe process known as INSTANT MASKING™ or INSTANT MASK™ plating.Selective depositions using conformable contact mask plating may be usedto form single layers of material or may be used to form multi-layerstructures. The teachings of the '630 patent are hereby incorporatedherein by reference as if set forth in full herein. Since the filing ofthe patent application that led to the above noted patent, variouspapers about conformable contact mask plating (i.e. INSTANT MASKING) andelectrochemical fabrication have been published:

-   -   1. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Batch production of functional, fully-dense metal        parts with micro-scale features”, Proc. 9th Solid Freeform        Fabrication, The University of Texas at Austin, p 161, August        1998.    -   2. A. Cohen, G. Zhang, F. Tseng, F. Mansfeld, U. Frodis and P.        Will, “EFAB: Rapid, Low-Cost Desktop Micromachining of High        Aspect Ratio True 3-D MEMS”, Proc. 12th IEEE Micro Electro        Mechanical Systems Workshop, IEEE, p 244, January 1999.    -   3. A. Cohen, “3-D Micromachining by Electrochemical        Fabrication”, Micromachine Devices, March 1999.    -   4. G. Zhang, A. Cohen, U. Frodis, F. Tseng, F. Mansfeld, and P.        Will, “EFAB: Rapid Desktop Manufacturing of True 3-D        Microstructures”, Proc. 2nd International Conference on        Integrated MicroNanotechnology for Space Applications, The        Aerospace Co., Apr. 1999.    -   5. F. Tseng, U. Frodis, G. Zhang, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, 3rd        International Workshop on High Aspect Ratio MicroStructure        Technology (HARMST'99), June 1999.    -   6. A. Cohen, U. Frodis, F. Tseng, G. Zhang, F. Mansfeld, and P.        Will, “EFAB: Low-Cost, Automated Electrochemical Batch        Fabrication of Arbitrary 3-D Microstructures”, Micromachining        and Microfabrication Process Technology, SPIE 1999 Symposium on        Micromachining and Microfabrication, September 1999.    -   7. F. Tseng, G. Zhang, U. Frodis, A. Cohen, F. Mansfeld, and P.        Will, “EFAB: High Aspect Ratio, Arbitrary 3-D Metal        Microstructures using a Low-Cost Automated Batch Process”, MEMS        Symposium, ASME 1999 International Mechanical Engineering        Congress and Exposition, November, 1999.    -   8. A. Cohen, “Electrochemical Fabrication (EFAB™)”, Chapter 19        of The MEMS Handbook, edited by Mohamed Gad-El-Hak, CRC Press,        2002.    -   9. “Microfabrication—Rapid Prototyping's Killer Application”,        pages 1-5 of the Rapid Prototyping Report, CAD/CAM Publishing,        Inc., June 1999.

The disclosures of these nine publications are hereby incorporatedherein by reference as if set forth in full herein.

The electrochemical deposition process may be carried out in a number ofdifferent ways as set forth in the above patent and publications. In oneform, this process involves the execution of three separate operationsduring the formation of each layer of the structure that is to beformed:

-   -   1. Selectively depositing at least one material by        electrodeposition upon one or more desired regions of a        substrate.    -   2. Then, blanket depositing at least one additional material by        electrodeposition so that the additional deposit covers both the        regions that were previously selectively deposited onto, and the        regions of the substrate that did not receive any previously        applied selective depositions.    -   3. Finally, planarizing the materials deposited during the first        and second operations to produce a smoothed surface of a first        layer of desired thickness having at least one region containing        the at least one material and at least one region containing at        least the one additional material.

After formation of the first layer, one or more additional layers may beformed adjacent to the immediately preceding layer and adhered to thesmoothed surface of that preceding layer. These additional layers areformed by repeating the first through third operations one or more timeswherein the formation of each subsequent layer treats the previouslyformed layers and the initial substrate as a new and thickeningsubstrate.

Once the formation of all layers has been completed, at least a portionof at least one of the materials deposited is generally removed by anetching process to expose or release the three-dimensional structurethat was intended to be formed.

The preferred method of performing the selective electrodepositioninvolved in the first operation is by conformable contact mask plating.In this type of plating, one or more conformable contact (CC) masks arefirst formed. The CC masks include a support structure onto which apatterned conformable dielectric material is adhered or formed. Theconformable material for each mask is shaped in accordance with aparticular cross-section of material to be plated. At least one CC maskis needed for each unique cross-sectional pattern that is to be plated.

The support for a CC mask is typically a plate-like structure formed ofa metal that is to be selectively electroplated and from which materialto be plated will be dissolved. In this typical approach, the supportwill act as an anode in an electroplating process. In an alternativeapproach, the support may instead be a porous or otherwise perforatedmaterial through which deposition material will pass during anelectroplating operation on its way from a distal anode to a depositionsurface. In either approach, it is possible for CC masks to share acommon support, i.e. the patterns of conformable dielectric material forplating multiple layers of material may be located in different areas ofa single support structure. When a single support structure containsmultiple plating patterns, the entire structure is referred to as the CCmask while the individual plating masks may be referred to as“submasks”. In the present application such a distinction will be madeonly when relevant to a specific point being made.

In preparation for performing the selective deposition of the firstoperation, the conformable portion of the CC mask is placed inregistration with and pressed against a selected portion of thesubstrate (or onto a previously formed layer or onto a previouslydeposited portion of a layer) on which deposition is to occur. Thepressing together of the CC mask and substrate occur in such a way thatall openings, in the conformable portions of the CC mask contain platingsolution. The conformable material of the CC mask that contacts thesubstrate acts as a barrier to electrodeposition while the openings inthe CC mask that are filled with electroplating solution act as pathwaysfor transferring material from an anode (e.g. the CC mask support) tothe non-contacted portions of the substrate (which act as a cathodeduring the plating operation) when an appropriate potential and/orcurrent are supplied.

An example of a CC mask and CC mask plating are shown in FIGS. 1(a)-1(c). FIG. 1( a) shows a side view of a CC mask 8 consisting of aconformable or deformable (e.g. elastomeric) insulator 10 patterned onan anode 12. The anode has two functions. FIG. 1( a) also depicts asubstrate 6 separated from mask 8. One is as a supporting material forthe patterned insulator 10 to maintain its integrity and alignment sincethe pattern may be topologically complex (e.g., involving isolated“islands” of insulator material). The other function is as an anode forthe electroplating operation. CC mask plating selectively depositsmaterial 22 onto a substrate 6 by simply pressing the insulator againstthe substrate then electrodepositing material through apertures 26 a and26 b in the insulator as shown in FIG. 1( b). After deposition, the CCmask is separated, preferably non-destructively, from the substrate 6 asshown in FIG. 1( c). The CC mask plating process is distinct from a“through-mask” plating process in that in a through-mask plating processthe separation of the masking material from the substrate would occurdestructively. As with through-mask plating, CC mask plating depositsmaterial selectively and simultaneously over the entire layer. Theplated region may consist of one or more isolated plating regions wherethese isolated plating regions may belong to a single structure that isbeing formed or may belong to multiple structures that are being formedsimultaneously. In CC mask plating as individual masks are notintentionally destroyed in the removal process, they may be usable inmultiple plating operations.

Another example of a CC mask and CC mask plating is shown in FIGS. 1(d)-1(f). FIG. 1( d) shows an anode 12′ separated from a mask 8′ thatcomprises a patterned conformable material 10′ and a support structure20. FIG. 1( d) also depicts substrate 6 separated from the mask 8′. FIG.1( e) illustrates the mask 8′ being brought into contact with thesubstrate 6. FIG. 1( f) illustrates the deposit 22′ that results fromconducting a current from the anode 12′ to the substrate 6. FIG. 1( g)illustrates the deposit 22′ on substrate 6 after separation from mask8′. In this example, an appropriate electrolyte is located between thesubstrate 6 and the anode 12′ and a current of ions coming from one orboth of the solution and the anode are conducted through the opening inthe mask to the substrate where material is deposited. This type of maskmay be referred to as an anodeless INSTANT MASK™ (AIM) or as ananodeless conformable contact (ACC) mask.

Unlike through-mask plating, CC mask plating allows CC masks to beformed completely separate from the fabrication of the substrate onwhich plating is to occur (e.g. separate from a three-dimensional (3D)structure that is being formed). CC masks may be formed in a variety ofways, for example, a photolithographic process may be used. All maskscan be generated simultaneously, prior to structure fabrication ratherthan during it. This separation makes possible a simple, low-cost,automated, self-contained, and internally-clean “desktop factory” thatcan be installed almost anywhere to fabricate 3D structures, leaving anyrequired clean room processes, such as photolithography to be performedby service bureaus or the like.

An example of the electrochemical fabrication process discussed above isillustrated in FIGS. 2( a)-2(f). These figures show that the processinvolves deposition of a first material 2 which is a sacrificialmaterial and a second material 4 which is a structural material. The CCmask 8, in this example, includes a patterned conformable material (e.g.an elastomeric dielectric material) 10 and a support 12 which is madefrom deposition material 2. The conformal portion of the CC mask ispressed against substrate 6 with a plating solution 14 located withinthe openings 16 in the conformable material 10. An electric current,from power supply 18, is then passed through the plating solution 14 via(a) support 12 which doubles as an anode and (b) substrate 6 whichdoubles as a cathode. FIG. 2( a), illustrates that the passing ofcurrent causes material 2 within the plating solution and material 2from the anode 12 to be selectively transferred to and plated on thecathode 6. After electroplating the first deposition material 2 onto thesubstrate 6 using CC mask 8, the CC mask 8 is removed as shown in FIG.2( b). FIG. 2( c) depicts the second deposition material 4 as havingbeen blanket-deposited (i.e. non-selectively deposited) over thepreviously deposited first deposition material 2 as well as over theother portions of the substrate 6. The blanket deposition occurs byelectroplating from an anode (not shown), composed of the secondmaterial, through an appropriate plating solution (not shown), and tothe cathode/substrate 6. The entire two-material layer is thenplanarized to achieve precise thickness and flatness as shown in FIG. 2(d). After repetition of this process for all layers, the multi-layerstructure 20 formed of the second material 4 (i.e. structural material)is embedded in first material 2 (i.e. sacrificial material) as shown inFIG. 2( e). The embedded structure is etched to yield the desireddevice, i.e. structure 20, as shown in FIG. 2( f).

Various components of an exemplary manual electrochemical fabricationsystem 32 are shown in FIGS. 3( a)-3(c). The system 32 consists ofseveral subsystems 34, 36, 38, and 40. The substrate holding subsystem34 is depicted in the upper portions of each of FIGS. 3( a) to 3(c) andincludes several components: (1) a carrier 48, (2) a metal substrate 6onto which the layers are deposited, and (3) a linear slide 42 capableof moving the substrate 6 up and down relative to the carrier 48 inresponse to drive force from actuator 44. Subsystem 34 also includes anindicator 46 for measuring differences in vertical position of thesubstrate which may be used in setting or determining layer thicknessesand/or deposition thicknesses. The subsystem 34 further includes feet 68for carrier 48 which can be precisely mounted on subsystem 36.

The CC mask subsystem 36 shown in the lower portion of FIG. 3( a)includes several components: (1) a CC mask 8 that is actually made up ofa number of CC masks (i.e. submasks) that share a common support/anode12, (2) precision X-stage 54, (3) precision Y-stage 56, (4) frame 72 onwhich the feet 68 of subsystem 34 can mount, and (5) a tank 58 forcontaining the electrolyte 16. Subsystems 34 and 36 also includeappropriate electrical connections (not shown) for connecting to anappropriate power source for driving the CC masking process.

The blanket deposition subsystem 38 is shown in the lower portion ofFIG. 3( b) and includes several components: (1) an anode 62, (2) anelectrolyte tank 64 for holding plating solution 66, and (3) frame 74 onwhich the feet 68 of subsystem 34 may sit. Subsystem 38 also includesappropriate electrical connections (not shown) for connecting the anodeto an appropriate power supply for driving the blanket depositionprocess.

The planarization subsystem 40 is shown in the lower portion of FIG. 3(c) and includes a lapping plate 52 and associated motion and controlsystems (not shown) for planarizing the depositions.

Another method for forming microstructures from electroplated metals(i.e. using electrochemical fabrication techniques) is taught in U.S.Pat. No. 5,190,637 to Henry Guckel, entitled “Formation ofMicrostructures by Multiple Level Deep X-ray Lithography withSacrificial Metal layers. This patent teaches the formation of metalstructure utilizing mask exposures. A first layer of a primary metal iselectroplated onto an exposed plating base to fill a void in aphotoresist, the photoresist is then removed and a secondary metal iselectroplated over the first layer and over the plating base. Theexposed surface of the secondary metal is then machined down to a heightwhich exposes the first metal to produce a flat uniform surfaceextending across the both the primary and secondary metals. Formation ofa second layer may then begin by applying a photoresist layer over thefirst layer and then repeating the process used to produce the firstlayer.

The process is then repeated until the entire structure is formed andthe secondary metal is removed by etching. The photoresist is formedover the plating base or previous layer by casting and the voids in thephotoresist are formed by exposure of the photoresist through apatterned mask via X-rays or UV radiation.

The '630 patent as well as the other conformable contact mask plating(i.e. Instant Mask Plating) and electrochemical fabrication (i.e. EFAB)publications noted above describe copper as a sacrificial material andnickel as a structural material. The copper is the preferred materialfor selective deposition while the nickel is the preferred material forblanket deposition. In most applications after formation of the nickelstructure it is desirable to reveal it by separating it from the coppersacrificial material. The '630 patent proposes that this removal beperformed by an etching operation and that useful etching compositionsfor selectively stripping copper from nickel structures include (1)solutions of ammonium hydroxide and copper sulfate or (2) solutions ofammonium hydroxide and sodium chlorite. This prior art patent indicatesthat a preferred etchant is Enstrip C38 commercially available fromEnthone OMI. The patent goes further and indicates that etching can alsobe performed in the presence of (1) vibrations, e.g., ultrasound appliedto the etchant or the substrate that was plated, and (2) pressurizedjets of etchant contacting the metal to be etched.

In September of 1998, Adam Cohen placed an enquiry onto the “mems-talk”mailing list at http://mail.mems-exchange.org. In this enquiry Mr. Cohenindicated that he was seeking suggestions concerning a Cu etchant thatdidn't cause pitting or other damage to Ni. He further indicated thatEnthone's Enstrip C38 caused pitting at least sometimes. In October of1998, Mr. Cohen received three responses to this enquiry: (1)recommendation to use a copper etching process that showed no pittingproblems with nickel—the etchant was HNO3:H3PO4:CH3COOH at 0.5:50.0:49.5(volume) and was used at room temperature; (2) recommendation to use acaustic etchant and in particular Cu(NH3)4++mixed with ammonia; and (3)recommendation to try 50% NH4OH mixed with 50% H2O2 in a 1:1 ratio.

A need remains in the field of conformable contact mask plating andelectrochemical fabrication (e.g. with contact masks or with adheredmasks) for improved post deposition processing and in particular forprocesses that separate copper from nickel or nickel alloys whileminimizing the pitting of nickel or nickel alloy structure), and moreparticularly to provide an improved process of separating copper oranother sacrificial material from nickel or nickel alloys when thenickel or nickel alloy structure has a complex geometry with sacrificialmaterial needing to be removed from small but extended or even intricatepassages within the nickel structure.

SUMMARY OF THE INVENTION

It is an object of certain aspects of the invention to provide improvedpost deposition processing for structures produced by conformablecontact mask plating or electrochemical fabrication.

It is an object of certain aspects of the invention to provide improvedpost deposition processing for structures produced using adhered masks.

It is an object of certain aspects of the invention to provide animproved process for separating a sacrificial material (e.g. copper)from nickel or from nickel alloys.

It is an object of certain aspects of the invention to provide animproved process for separating a copper from a structural material (e.ga nickel or nickel alloy).

It is an object of certain aspects of the invention to provide ageneralized sacrificial material (e.g. copper or copper alloy) removalprocess that can be used to remove the sacrificial material from acomplex structure that includes nickel or nickel alloy without damagingthe nickel or nickel alloy.

Other objects and advantages of various aspects of the invention will beapparent to those of skill in the art upon review of the teachingsherein. The various aspects of the invention, set forth explicitlyherein or otherwise ascertained from the teachings herein, may addressany one of the above objects alone or in combination, or alternativelymay not address any of the objects set forth above but instead addresssome other object that may be ascertainable from the teachings herein.It is not intended that all of these objects be addressed by any singleaspect of the invention even though that may be the case with regard tosome aspects.

A first aspect of the invention provides an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers, the process that includes: (A) selectively depositing afirst material onto a substrate to form a portion of a layer anddepositing at least a second material to form another portion of thelayer, wherein the substrate may comprise previously deposited material,and wherein one of the first material or the second material is astructural material and the other is a sacrificial material; (B) forminga plurality of layers such that each successive layer is formed adjacentto and adhered to a previously deposited layer, wherein said formingcomprises repeating operation (A) a plurality times, wherein duringformation of at least one layer an adhered mask is used in selectivelydepositing the first material; and (C) after formation of a plurality oflayers, separating at least a portion of the sacrificial material fromthe structural material using an etching solution that comprisesammonium hydroxide, a chlorite salt, and a nitrate salt.

A second aspect of the invention provides a process for anelectrochemical fabrication process for producing a three-dimensionalstructure from a plurality of adhered layers, the process including: (A)selectively patterning a first material on a substrate to form a portionof a layer and depositing at least a second material to form anotherportion of the layer, wherein the substrate may comprise previouslydeposited material, and wherein one of the first material or the secondmaterial is a structural material and the other is a sacrificialmaterial; (B) forming a plurality of layers such that each successivelayer is formed adjacent to and adhered to a previously deposited layer,wherein said forming comprises repeating operation (A) a pluralitytimes, wherein during formation of at least one layer an adhered mask isused in selectively patterning the first material; and (C) afterformation of a plurality of layers, separating at least a portion of thesacrificial material from the structural material using an etchingsolution that comprises ammonium hydroxide, a chlorite salt, and anitrate salt.

A third aspect of the invention provides an electrochemical fabricationprocess for producing a three-dimensional structure from a plurality ofadhered layers, the process comprising: (A) selectively depositing afirst material onto a substrate to form a portion of a layer anddepositing at least a second material to form another portion of thelayer, wherein the substrate may comprise previously deposited material,and wherein one of the first material or the second material is astructural material and the other is a sacrificial material; (B) forminga plurality of layers such that each successive layer is formed adjacentto and adhered to a previously deposited layer, wherein said formingcomprises repeating operation (A) a plurality times, wherein duringformation of at least one layer an adhered mask is used in selectivelydepositing the first material; and (C) after formation of a plurality oflayers, separating at least a portion of the sacrificial material fromthe structural material using an etching solution that comprises acorrosion inhibitor.

Further aspects of the invention will be understood by those of skill inthe art upon reviewing the teachings herein. Other aspects of theinvention may involve combinations of the above noted aspects of theinvention and/or addition of various features of one or moreembodiments. Other aspects of the invention may involve apparatus thatcan be used in implementing one or more of the above method aspects ofthe invention. These other aspects of the invention may provide variouscombinations of the aspects presented above as well as provide otherconfigurations, structures, functional relationships, and processes thathave not been specifically set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a)-1(c) schematically depict side views of various stages of aCC mask plating process, while FIGS. 1( d)-(g) schematically depict aside views of various stages of a CC mask plating process using adifferent type of CC mask.

FIGS. 2( a)-2(f) schematically depict side views of various stages of anelectrochemical fabrication process as applied to the formation of aparticular structure where a sacrificial material is selectivelydeposited while a structural material is blanket deposited.

FIGS. 3( a)-3(c) schematically depict side views of various examplesubassemblies that may be used in manually implementing theelectrochemical fabrication method depicted in FIGS. 2( a)-2(f).

FIGS. 4( a)-4(i) schematically depict the formation of a first layer ofa structure using adhered mask plating where the blanket deposition of asecond material overlays both the openings between deposition locationsof a first material and the first material itself.

FIG. 5 depicts a table of copper etchants and various propertiesassociated with them.

FIG. 6 depicts a plot of etching rate versus C-38 copper stripperconcentration.

FIG. 7 depicts a scanning electron microscope image of a nickelstructure damaged by an etchant process that included excessivevibration.

FIG. 8 depicts a nickel structure that was pitted by etching with C-38.

FIG. 9 depicts a plot of etched length of a copper wire versus etchingtime.

DETAILED DESCRIPTION

FIGS. 1( a)-1(g), 2(a)-2(f), and 3(a)-3(c) illustrate various featuresof one form of electrochemical fabrication that are known. Otherelectrochemical fabrication techniques are set forth in the '630 patentreferenced above, in the various previously incorporated publications,in various other patents and patent applications incorporated herein byreference, still others may be derived from combinations of variousapproaches described in these publications, patents, and applications,or are otherwise known or ascertainable by those of skill in the artfrom the teachings set forth herein. All of these techniques may becombined with those of the various embodiments of various aspects of theinvention to yield enhanced embodiments. Still other embodiments be mayderived from combinations of the various embodiments explicitly setforth herein.

FIGS. 4( a)-4(i) illustrate various stages in the formation of a singlelayer of a multi-layer fabrication process where a second metal isdeposited on a first metal as well as in openings in the first metalwhere its deposition forms part of the layer. In FIG. 4( a), a side viewof a substrate 82 is shown, onto which patternable photoresist 84 iscast as shown in FIG. 4( b). In FIG. 4( c), a pattern of resist is shownthat results from the curing, exposing, and developing of the resist.The patterning of the photoresist 84 results in openings or apertures92(a)-92(c) extending from a surface 86 of the photoresist through thethickness of the photoresist to surface 88 of the substrate 82. In FIG.4( d), a metal 94 (e.g. nickel) is shown as having been electroplatedinto the openings 92(a)-92(c). In FIG. 4( e), the photoresist has beenremoved (i.e. chemically stripped) from the substrate to expose regionsof the substrate 82 which are not covered with the first metal 94. InFIG. 4( f), a second metal 96 (e.g., silver) is shown as having beenblanket electroplated over the entire exposed portions of the substrate82 (which is conductive) and over the first metal 94 (which is alsoconductive). FIG. 4( g) depicts the completed first layer of thestructure which has resulted from the planarization of the first andsecond metals down to a height that exposes the first metal and sets athickness for the first layer. In FIG. 4( h) the result of repeating theprocess steps shown in FIGS. 4( b)-4(g) several times to form amulti-layer structure are shown where each layer consists of twomaterials. For most applications, one of these materials is removed asshown in FIG. 4( i) to yield a desired 3-D structure 98 (e.g. componentor device).

In some preferred conformable contact mask plating and electrochemicalfabrication embodiments, deposition and etching of a sacrificialmaterial, such as copper, are essential steps. The sacrificial materialserves as a mechanical support of the structural material duringstructure formation. Additionally, since the sacrificial material, likethe structural material, is conductive, additional material can bedeposited over the entire layer without constraint. Thus the use of asacrificial material eliminates virtually all geometrical restrictions,allowing the structural material on a layer to overhang and even bedisconnected from that of the previous layer. Furthermore, the use of asacrificial material may allow a broader range of structural materialsto be used in that the sacrificial material can be deposited in aselective process (e.g. by a conformable contact mask process) while thestructural material may be deposited in some other manner (e.g. blanketdeposition) where fewer deposition limitations may exist.

The basic rules governing etching are as follows:

1. Selectivity: Etchants should only remove sacrificial materials. No orlittle effect on main materials should occur.

2. Completion: A sacrificial material needs to be removed completely.

3. Speed: The less the etching time the higher the throughput.

4. Integration: An etching process should not damage delicatestructures.

Wet etching is a fast, cheap process and can also remove materials fromblind geometries. Usually, to remove a metal, it must be of an oxidizedform so as to transition from the metallic to an ionic state. Therefore,the active ingredient in a metal etchant needs to be an oxidizing agent.Alternatively, electrochemical anodic etching provides the requiredoxidizing action by passing a current of cations from a work piece. Anacid or alkaline complexing agent may be included to increase theetching rate. Other additives may also be included. Common oxidizingagents used for stripping copper include chlorite, ferric chloride,cupric chloride, persulfate, organic nitro compounds, and peroxide.

In electrochemical fabrication, a fast reliable copper etching processwithout negative effect on structural material (e.g. nickel) andassociated structures desired necessary to achieve the final structures(e.g. microstructures).

Some common copper etchants were evaluated for use in electrochemicalfabrication and are listed in FIG. 5. In the evaluation (1) etchingrates for the etchants were determined from either tests or fromreferences, (2) Ni compatibility was determined, and (3) the etchingprocesses for each etchant were examined. Copper foil samples were usedfor measuring etching rates and had dimensions of 2 cm×4 cm×60 μm and apurity of 99.5%. To hold the samples in the etchant solutions, a holewas drilled with a diameter of 0.48 cm in each sample. Etching time wasvariable depending on actual reaction rate of each etchant at roomtemperature (˜20° C.). The etching rate in each etchant was determinedfrom the difference in measured weight of the copper foil before andafter the test.

Although these etchants were reported to be nickel compatible, etchantswith slow etching rate and bubble formation during the etching processwere not considered further. A slow etching rate means more process timewhile vigorous bubble formation could induce stress in free standingstructures such as beams and cantilevers, could break delicatemicrostructures, or could inhibit etchant access into small passages.Though most of the etchants were successful in removing thin sacrificialcopper films, their slow etching rates and/or bubble formation make themimpractical for removing relatively large amounts of copper inelectrochemical fabrication or similar cases. Of the etchants evaluatedthe ENSTRIP® C-38 stripper had an etching rate of 460 μm/hr and appearedto be the most promising.

ENSTRIP® C-38 stripper (Enthone-OMI Inc. of New Haven, Conn.) is atwo-component, ammoniacal immersion stripper designed to quickly removecopper from steel and stainless steel substrates. The recommended C-38stripper is formed from two primary components, Enstrip C-38A at 75% byvolume and Enstrip C-38B at 25% by volume. It is recommended that theEnstrip C-38 solution should only be operated within the pH range of 9.3to 10.5 and within a temperature range from room temperature to amaximum of 38° C. If the solution pH becomes too low, it is recommendedthat 27% ammonium hydroxide be added in small increments until the pH isbrought into the right range. It is believed that the two maincomponents of the C-38 solution are sodium chlorite, NaClO2, andammonium hydroxide, NH4OH. The C-38 solution can dissolve up to 8 ouncesof copper per gallon of solution. The C-38 basic reaction mechanism isbelieved to be:

On the etching surface:

ClO₂ ⁻+H₂O+2e→ClO⁻+2OH⁻

2Cu−2e→2Cu⁺

Cu⁺+2NH₃→[Cu(NH₃)₂]⁺

In the bulk solution:

ClO₂ ⁻+H₂O+2e→ClO⁻+2OH⁻

2[Cu(NH₃)₂]⁺+4NH₃−2e→2[Cu(NH₃)₄]²⁺

C-38 does not attack nickel significantly. Experiments showed that thenickel corrosion rate in C-38 is only about 72 μm/yr. For a shortetching time, the actual amount of etched nickel is negligible. Toextend the range of electrochemical fabrication structural materialsbeyond nickel, the etching rates of other metals and alloys were testedin C-38. Samples with a known area and weight were immersed into C-38 atroom temperature for a known time. The etching rate was calculated fromthe corresponding weight loss. The test results are listed in thefollowing table.

Compatibility of Metals and Alloys in C-38 Testing Etching Rate in C38at 20° C. Material Form of Material (μm/hr) Cu Cu foil, 99.5% ~460 Ni NiDeposit from Ni sulfamate ~0 bath Fe Mild steel, >99% 0.02 Au GoldMirror ~0 Ag Silver wire, 99.99% 0.41 Pt Platinum wire ~0 Sn Tin round,99.85% 0.02 Pb Lead wire, 99.92% 0.08 Zn Zinc wire, 99.9% Dissolvedquickly Sn—Ag Solder wire, 96%-4% 0.02 Pd—Sn Solder wire, 60%-40% 0.10Fe—Ni ~0

Zinc is not suitable for use as an unprotected structural material butmay be useful as a sacrificial material since it is quickly dissolved inC-38. All other metals and alloys that were tested were determined to beuseful as structural materials when C-38 is the etchant.

The etching rate of copper in C-38 can be adjusted downward by dilutingthe full strength C-38. A plot of etching rates versus C-38concentration is shown in FIG. 6. For real microstructure release, theetching rate will be lower and will depend on actual geometriccomplexity since an etching rate is determined by rates of (1) freshetchant delivery to etching surface and (2) reaction products deliveryto the bulk solution. For example, one experiment indicated that theetching rate of an epoxy embedded copper wire with a diameter of 0.64 mmwas only about 180 μm/hr for first two hours. Stirring the etchantsolution improved etching rate. One test showed that the etching ratefor copper wires (d=0.64 mm) embedded in epoxy in C-38 at 36° C. whenultrasonically stirred (i.e. agitated) was 2.7 times as large as thatwhen stirring with a magnetic stirring bar during a 24 hour period.Although stirring or agitating can improve etching rates, if too violentsuch as by excess ultrasonic agitation damage to microstructures canresult. An example of what excess stirring can do to structures producedby electrochemical fabrication is shown in the scanning electronmicroscope (SEM) image of FIG. 7, in which ultrasonic stirring was usedto help release the microstructure. It appears that the vibrationruptured the structure at edge 102 of the nickel deposit 104 on nickelsubstrate 106. As opposed to the vibrations themselves being tooviolent, another possible explanation is that the frequency of thevibrations excited resonance in the deposited structure which resultedin its failure.

The C-38 wet etching process is followed by a drying process to removethe liquid in the microstructure. Because of the surface tension of therinse water, the released free-standing structures can tend to stick tothe substrate. Once a structure is attached to the substrate bysticking, the mechanical force needed to dislodge it usually is largeenough to damage the structure. In some MEMS processes, it has beenproposed that this problem be overcome by use of freezing-sublimation ora CO2 supercritical drying process. However, these techniques can beprocess intensive, time consuming and often require sophisticatedhigh-pressure apparatus. In electrochemical fabrication, a relativelysimple method is preferred. After rinsing the part, it is immediatelytransferred into an alcohol solution where the alcohol is made toreplaces the water in the structure. The structure is then immediatelytransferred to an oven at ˜60° C. for 5-10 minutes to evaporate thealcohol and dry the structure.

The preferred procedure for releasing structures (i.e. copper fromnickel structures) produced by electrochemical fabrication involvessurrounding the combined copper/nickel structure with a diluted C-38etchant without any stirring. The preferred dilution is about one partC-38 by volume to about four to five parts H2O. In some embodimentsthough, the level of dilution may range from as low as about one partC-38 to about ten parts waters and as high as undiluted C-38. Theetching endpoint is reached when a blue substance stops appearing fromthe structure and in particular from any cavity ports within thestructure. The structure is then dipped into a Di water tank and isslowly moved through the water so as to displace the etchant with thewater. The structure is then transferred to an alcohol tank where thestructure is slowly moved through the alcohol to displace the water withalcohol and it is thereafter removed from the tank and dried in an oven.

Ni is considered to be a slightly noble metal. It resists corrosion inmany environments due to its high passivation tendency. Usually there isa passive oxide or hydrated oxide film on the nickel surface whichproduces good corrosion resistance. In neutral and moderately alkalinesolutions, a passive surface layer of Ni(OH)2 and perhaps NiO forms onnickel surface, while the passive film is possibly NiOOH in stronglyoxidizing neutral and alkaline conditions such as in a C-38 environment(i.e. in an alkaline oxidizing solution).

Passive films protecting metals and alloys break down locally in certaincorrosion environments and pitting results. Local points undergo anodicdissolution to form pits on the surface, while the major part of thesurface remains passive. Usually, the diameter of pits is in the rangeof tens of micrometers and the depth of pits is equal to or more thantheir diameter. Obviously, formation of pits on nickel is unacceptableto microstructures. C-38 works well in etching copper without attackingnickel. However, occasionally pits have been observed to form on thenickel substrate and nickel deposits. FIG. 8 shows an SEM image of pitson a nickel deposit. A possible explanation for these phenomena is thatchlorite is not very stable and could decompose by light, temperatureand catalysts to produce hypochlorite and/or chloride ions, especiallyfor aged or used C-38 solutions. In addition, as indicated in the abovebasic reaction equations hypochlorite is also produced during theetching process. Hypochlorite could attack nickel to form pits. Based onthese possibilities, some preferred electrochemical fabrication etchingprocesses involving C-38 include one or more of, and more preferably allof, (1) minimizing the C-38's contact with light, high temperature, orair during its storage period; (2) mixing the two components just beforeetching to ensure the freshness of the etchant; (3) checking the pH ofthe C-38 prior to each use to make sure it has a pH between 9.3 and10.5.

Additional preferred electrochemical fabrication etching processes add acorrosion inhibitor to the C-38 to help prevent pitting. The use of acorrosion inhibitor in combination with the etchant may be done in aloneor in addition to the above noted handling and checking preferences. Thepreferred inhibitor for use in etching electrochemical fabricationstructures with a chlorite based etchant like C-38 is sodium nitrate,NaNO3.

Corrosion inhibitors are chemical compounds which, when added in smallconcentration to a corrosion environment, can greatly increase thecorrosion resistance of an exposed metal. It is known that nitrate canbe used as a pitting inhibitor for steels, stainless steels, aluminumand its alloys, and for nickel. For nickel, it is believed that theanti-pitting mechanism of NaNO3 is due to the preferential adsorption ofNO3− on the nickel surface. In this way, NO3− ions prevent aggressiveions like ClO− from adsorbing on the surface to cause pitting. Thepresence of the nitrate can shift a pitting potential (Epit) to a morenoble value. Its efficiency can be evaluated by a pitting scan which isa potentiodynamic polarization curve measurement in which Epit isdetermined from the anodic polarization curve as the potential where thecurrent density sharply increases due to breakdown of the passive filmand formation of pits. Pits initiate and grow above Epit, but not below.The more positive the Epit, the better the efficiency of the inhibitor.

A test was performed to determine if the present of NaNO3 could raisethe Epit value. The test was performed using polished nickel diskshaving diameters of 1.27 cm. Pitting scans were conducted in 0.5 N NaClwith and without NaNO3 (1 g/100 ml) using an EG&G 273APotentiostat/Galvanostat in accordance with ASTM G5 and G61. The scanrate was 0.166 mV/s. Polarization curves with and without NaNO3 areshown in FIG. 8. Epit increased by about 90 mV in the presence of 1 gNaNO3/100 mL of NaNO3. An additional test indicated that when only 0.1g/100 ml NaNO3 was added, no shift of Epit occurred. It is believed thata concentration of NaNO3 sufficient to raise the Epit value by about 10mV would yield some improvement in performance though having it beraised to about 30 mV or more preferably by about 50 mV would be better.In any event, an effective quantity of an antipitting agent may beempirically determined by those of skill in the art in view of theteachings herein such that pitting is eliminated or brought down to atolerable level.

An experiment was performed to determine the effect of the presence ofNaNO3 on the copper etching rate. The determined etching rate of copperfoil in C-38 containing 1 g/100 ml NaNO3 was 430 μm/hr compared to 460μm/hr without NaNO3 suggesting that the presence of NaNO3 has only asmall effect on copper etching and that the effectiveness of the etchantremains. Experiments have also shown that pitting is reduced whenetching with C-38 in combination with a small amount of NaNO3 (sodiumnitrate). It is believed that the concentration of C-38 may be loweredto about 0.5 g/100 ml and still have obtain a benefit from the processand raised well above the 1 g/100 ml concentration level withoutbringing harm to the etching process though a point may be reached wherelittle additional benefit is added by the increased concentration.

Wet chemical sacrificial etching is dependent on the reacting speciesreaching the etching surface (e.g. by diffusion). If the etching area isrelatively large and open to the etchant, and the etching length of thesacrificial layer is short (e.g. <100 μm), the etchant can always besufficiently supplied at the etching front. This etching mode is calledreaction-limited etching. However, if the etching length is very longcompared to the channel width such as in channel etching or where theetchant flow is severely restricted due to cavities or structures withirregularly shaped interfaces, the etchant may be depleted at theetching front. This is known as the diffusion-limited etching mode. Inthis mode, etching may become extremely slow or even stop. FIG. 9depicts a plot of etched copper length versus time in a one-dimensionaletching test that was carried out in C-38 at 38° C. aided by ultrasonicstirring for a 40 μm diameter copper wire (one end of an epoxy embeddedcopper wire is exposed to the etchant). With time, the etching ratedramatically decreased and after 5 hours, etching practically stopped.

To eliminate the limitation of diffusion of chemical species in wetchemical etching, it is believed that some form of electrochemicalanodic etching may be used to assist in the removal of copperparticularly from complex geometries such as narrow passages and blindcavities. Besides the chemical etching effect of an etchant itself oncopper, electrochemical anodic etching provides also for anodicdissolution by passing current through the etchant to the surface to beetched. In addition, the applied electric field can drive copper ionsthrough the etchant away from the structure being etched toward acathode while simultaneously attracting anions to the surface of thestructure, thus creating higher material transfer rate and helping tobring unreacted fluid closer to the copper front due to conservation ofmass.

Preliminary electrochemical anodic etching of both the DC and biased ACtype were investigated for use with electrochemical fabrication producedstructures. C-38 was used as the etchant. Based on these preliminaryinvestigations, electrochemical etching seems to be a promising copperetching technique.

The patent applications and patents set forth below are herebyincorporated by reference herein as if set forth in full. The teachingsin these incorporated applications can be combined with the teachings ofthe instant application in many ways: For example, enhanced methods ofproducing structures may be derived from some combinations of teachings,enhanced structures may be obtainable, enhanced apparatus may bederived, and the like.

US Pat App No, Filing Date US App Pub No, Pub Date Inventor, Title09/493,496 - Jan. 28, 2000 Cohen, “Method For ElectrochemicalFabrication” 10/677,556 - Oct. 1, 2003 Cohen, “Monolithic StructuresIncluding Alignment and/or Retention Fixtures for Accepting Components”10/830,262 - Apr. 21, 2004 Cohen, “Methods of Reducing InterlayerDiscontinuities in Electrochemically Fabricated Three- DimensionalStructures” 10/841,300 - May 7, 2004 Lockard, “Methods forElectrochemically Fabricating (Docket P-US099-A-MF) Structures UsingAdhered Masks, Incorporating Dielectric Sheets, and/or Seed layers ThatAre Partially Removed Via Planarization” 10/271,574 - Oct. 15, 2002Cohen, “Methods of and Apparatus for Making High 2003-0127336A - Jul.10, 2003 Aspect Ratio Microelectromechanical Structures” 10/697,597 -Dec. 20, 2002 Lockard, “EFAB Methods and Apparatus Including Spray Metalor Powder Coating Processes” 10/677,498 - Oct. 1, 2003 Cohen,“Multi-cell Masks and Methods and Apparatus for Using Such Masks To FormThree-Dimensional Structures” 10/724,513 - Nov. 26, 2003 Cohen,“Non-Conformable Masks and Methods and Apparatus for FormingThree-Dimensional Structures” 10/607,931 - Jun. 27, 2003 Brown,“Miniature RF and Microwave Components and Methods for Fabricating SuchComponents” 10/841,100 - May 7, 2004 Cohen, “Electrochemical FabricationMethods (Docket P-US093-A-MF) Including Use of Surface Treatments toReduce Overplating and/or Planarization During Formation of Multi-layerThree-Dimensional Structures” 10/387,958 - Mar. 13, 2003 Cohen,“Electrochemical Fabrication Method and 2003-022168A - Dec. 4, 2003Application for Producing Three-Dimensional Structures Having ImprovedSurface Finish” 10/434,494 - May 7, 2003 Zhang, “Methods and Apparatusfor Monitoring 2004-0000489A - Jan. 1, 2004 Deposition Quality DuringConformable Contact Mask Plating Operations” 10/434,289 - May 7, 2003Zhang, “Conformable Contact Masking Methods and 20040065555A - Apr. 8,2004 Apparatus Utilizing In Situ Cathodic Activation of a Substrate”10/434,294 - May 7, 2003 Zhang, “Electrochemical Fabrication MethodsWith 2004-0065550A - Apr. 8, 2004 Enhanced Post Deposition ProcessingEnhanced Post Deposition Processing” 10/434,295 - May 7, 2003 Cohen,“Method of and Apparatus for Forming Three- 2004-0004001A - Jan. 8, 2004Dimensional Structures Integral With Semiconductor Based Circuitry”10/434,315 - May 7, 2003 Bang, “Methods of and Apparatus for Molding2003-0234179 A - Dec. 25, Structures Using Sacrificial Metal Patterns”2003 10/434,103 - May 7, 2004 Cohen, “Electrochemically FabricatedHermetically 2004-0020782A - Feb. 5, 2004 Sealed Microstructures andMethods of and Apparatus for Producing Such Structures” 10/841,006 - May7, 2004 Thompson, “Electrochemically Fabricated Structures (DocketP-US104-A-MF) Having Dielectric or Active Bases and Methods of andApparatus for Producing Such Structures” 10/434,519 - May 7, 2003Smalley, “Methods of and Apparatus for 2004-0007470A - Jan. 15, 2004Electrochemically Fabricating Structures Via Interlaced Layers or ViaSelective Etching and Filling of Voids” 10/724,515 - Nov. 26, 2003Cohen, “Method for Electrochemically Forming Structures IncludingNon-Parallel Mating of Contact Masks and Substrates” 10/841,347 - May 7,2004 Cohen, “Multi-step Release Method for (Docket P-US105-A-MF)Electrochemically Fabricated Structures”

Various other embodiments of the present invention exist. Some of theseembodiments may be based on a combination of the teachings herein withvarious teachings incorporated herein by reference. Some embodiments maynot use any blanket deposition process and/or they may not use aplanarization process. Some embodiments may involve the selectivedeposition of a plurality of different materials on a single layer or ondifferent layers. Some embodiments may use blanket depositions processesthat are not electrodeposition processes. Some embodiments may useselective deposition processes on some layers that are not Instant Maskprocesses and are not even electrodeposition processes.

Some embodiments may use nickel as a structural material. Someembodiments may use nickel alloys as a structural material, such asnickel-phosphorous (NiP), nickel-cobalt (NiC), nickel-iron (NiFe),nickel-manganese (NiMn), and the like. Some embodiments may use adifferent material or alloy as a structural material, e.g. gold, tin orsolder, or any other material or materials that can be separated from asacrificial material (e.g. copper, zinc, silver, alloys of thesematerials, or the like). The structural material and/or the sacrificialmaterial may be electrodepositable, electroplatable, or depositable insome other manner. In some embodiments, the nitrate salt used as acorrosion or pitting inhibitor may be different from sodium nitrate,e.g. it may be ammonium nitrate or potassium nitrate. 6

In some embodiments instead of using a nitrate salt as discussed aboveit may be possible to use other corrosion inhibitors or pittinginhibitors such as for example:

1. Sulfate salts such as potassium sulfate, sodium sulfate and ammoniumsulfate;

2. Phosphate salts such as potassium phosphate, sodium phosphate andammonium phosphate (e.g. phosphate, monobasic and phosphate, dibasic);

3. Carbonate salts such as potassium carbonate, sodium carbonate andammonium carbonate (in some alternatives, carbonate may be replaced bybicarbonate);

4. Molybdate salts such as potassium molybdate, sodium molybdate andammonium molybdate; and

5. Silicate salts such as potassium silicate, sodium silicate andammonium silicate.

In some embodiments the various corrosion inhibitors mentioned hereinmay be used in combination.

In some embodiments the anode may be different from a CC mask supportand the support may be a porous structure or other perforated structure.Some embodiments will use multiple masks (e.g. CC masks or adhered maskswith different patterns so as to deposit different selective patterns ofmaterial on different layers and/or on different portions of a singlelayer. In some embodiments, the depth of deposition may be enhanced bypulling the CC mask away from the substrate as deposition is occurringin a manner that allows the seal between the conformable portion of theCC mask and the substrate to shift from the face of the conformalmaterial to the inside edges of the conformable material.

In view of the teachings herein, many further embodiments, alternativesin design and uses of the instant invention will be apparent to those ofskill in the art. As such, it is not intended that the invention belimited to the particular illustrative embodiments, alternatives, anduses described above but instead that it be solely limited by the claimspresented hereafter.

1. An electrochemical fabrication process for producing athree-dimensional structure from a plurality of adhered layers, theprocess comprising: (A) selectively depositing a first material onto asubstrate to form a portion of a layer and depositing at least a secondmaterial to form another portion of the layer, wherein the substrate maycomprise previously deposited material, and wherein one of the firstmaterial or the second material is a structural material and the otheris a sacrificial material; (B) forming a plurality of layers such thateach successive layer is formed adjacent to and adhered to a previouslydeposited layer, wherein said forming comprises repeating operation (A)a plurality times, wherein during formation of at least one layer anadhered mask is used in selectively depositing the first material; and(C) after formation of a plurality of layers, separating at least aportion of the sacrificial material from the structural material usingan etching solution that comprises ammonium hydroxide, a chlorite salt,and a nitrate salt.
 2. The process of claim 1 additionally comprising:(D) supplying a plurality of preformed masks, wherein each maskcomprises a patterned dielectric material that includes at least oneopening through which deposition can take place during the formation ofat least a portion of a layer, and wherein each mask comprises a supportstructure that supports the patterned dielectric material; and whereinat least a plurality of the selective depositing operations comprise:(1) contacting the substrate and the dielectric material of a selectedpreformed mask or proximately locating the substrate and dielectricmaterial of the selected preformed mask; (2) in presence of a platingsolution, conducting an electric current through the at least oneopening in the selected mask between an anode and the substrate, whereinthe anode comprises a selected deposition material, and wherein thesubstrate functions as a cathode, such that the selected depositionmaterial is deposited onto the substrate to form at least a portion of alayer; and (3) separating the selected preformed mask from thesubstrate.
 3. The process of claim 1 wherein a plurality of selectivedepositing operations comprise: (1) adhering a mask having a desiredpattern to the substrate, wherein the mask includes at least oneopening; (2) in presence of a plating solution, conducting an electriccurrent through the at least one opening in the adhered mask between ananode and the substrate, wherein the anode comprises a selecteddeposition material, and wherein the substrate functions as a cathode,such that the selected deposition material is deposited onto thesubstrate to form at least a portion of a layer; and (3) separating themask from the substrate.
 4. The process of claim 2 wherein the platingsolution is at a temperature below about 43° C. when conduction of theelectric current begins.
 5. The process of claim 2 wherein the platingsolution is at a temperature below about 38° C. when conduction of theelectric current begins.
 6. The process of claim 2 wherein the platingsolution is not agitated during selective deposition.
 7. The process ofclaim 1 wherein the formation of each of a number of layers comprise atleast one blanket deposition as well as the selective deposition whereinfor a given layer the selectively deposited material is different from amaterial deposited by blanket deposition.
 8. The process of claim 1wherein the plurality of selective depositions comprise the depositionof a plurality of different materials.
 9. The process of claim 1 whereinat least a portion of one layer is formed by a non-electroplatingdeposition process.
 10. The process of claim 1 wherein a plurality ofdepositions occur during the formation of each of a number of layerswherein at least one of the depositions on each of the number of layersdeposits copper and at least one of the other depositions on the numberof layers deposits nickel.
 11. The process of claim 1 wherein theselective depositing for each of a number of layers comprises at leasttwo selective depositions.
 12. The process of claim 1 wherein a numberof the plurality of layers are each formed by depositing at least onestructural material using at least one deposition and by depositing atleast one sacrificial material by using at least one other deposition.13. The process of claim 12 wherein at least a portion of the at leastone sacrificial material is removed after formation of a plurality oflayers to reveal a three-dimensional structure comprised of at least onestructural material.
 14. The process of claim 2 wherein, for each of aplurality of masks, the support for the dielectric material for a maskcomprises the anode involved in the deposition associated with the useof the mask.
 15. The process of claim 2 wherein, for each of a pluralityof masks, the support for the dielectric material for a mask is a porousmedium which does not act as the anode during involved in the depositionassociated with the use of the mask.
 16. The process of claim 1 whereinthe formation of at least a plurality of layers additionally comprisesremoving a portion of the deposited material from the substrate suchthat a desired surface level is obtained.
 17. The process of claim 1wherein the at least one sacrificial material comprises copper.
 18. Theprocess of claim 1 wherein the at least one structural materialcomprises nickel.
 19. The process of claim 1 wherein the chlorite saltin the etching solution comprises sodium chlorite.
 20. The process ofclaim 1 wherein the nitrate salt comprises sodium nitrate
 21. Theprocess of claim 1 wherein during etching, the structure and etchant aremoved relative to one another.
 22. The process of claim 1 wherein theetching process is aided by application of an electric potential betweenthe substrate and an electrode immersed in the etching solution.
 23. Anelectrochemical fabrication process for producing a three-dimensionalstructure from a plurality of adhered layers, the process comprising:(A) selectively patterning a first material on a substrate to form aportion of a layer and depositing at least a second material to formanother portion of the layer, wherein the substrate may comprisepreviously deposited material, and wherein one of the first material orthe second material is a structural material and the other is asacrificial material; (B) forming a plurality of layers such that eachsuccessive layer is formed adjacent to and adhered to a previouslydeposited layer, wherein said forming comprises repeating operation (A)a plurality times, wherein during formation of at least one layer anadhered mask is used in selectively patterning the first material; and(C) after formation of a plurality of layers, separating at least aportion of the sacrificial material from the structural material usingan etching solution that comprises ammonium hydroxide, a chlorite salt,and a nitrate salt.
 24. The process of claim 23 wherein the at least onesacrificial material comprises copper and the at least one structuralmaterial comprises nickel.
 25. The process of claim 23 wherein thechlorite salt in the etching solution comprises sodium chlorite.
 26. Theprocess of claim 23 wherein the nitrate salt comprises sodium nitrate27. The process of claim 23 wherein during etching, the structure andetchant are moved relative to one another.
 28. The process of claim 23wherein the etching process is aided by application of an electricpotential between the substrate and an electrode immersed in the etchingsolution.
 29. An electrochemical fabrication process for producing athree-dimensional structure from a plurality of adhered layers, theprocess comprising: (A) selectively depositing a first material onto asubstrate to form a portion of a layer and depositing at least a secondmaterial to form another portion of the layer, wherein the substrate maycomprise previously deposited material, and wherein one of the firstmaterial or the second material is a structural material and the otheris a sacrificial material; (B) forming a plurality of layers such thateach successive layer is formed adjacent to and adhered to a previouslydeposited layer, wherein said forming comprises repeating operation (A)a plurality times, wherein during formation of at least one layer anadhered mask is used in selectively depositing the first material; and(C) after formation of a plurality of layers, separating at least aportion of the sacrificial material from the structural material usingan etching solution that comprises a corrosion inhibitor.